Re: Using two radios on the same band de N4KG
The first thing to determine is how much power is coupled from
one antenna to the other. Worst case will be with the two antennas
pointed towards each other. This can be measured by transmitting
into one antenna with a wattmeter and dummy load connected to
the other. Many years ago, I conducted a similar experiment with
two 15M beams spaced approximately 70 ft. Using 1000W, the
second antenna received only 5 watts.
For receiver protection, I built an in-line box with 22 ohms series
resistance (2W) followed by two stacks of 4 diodes in oppositite
polarity. I have never again damaged a receiver front end. The
less coupling between antennas, the better you will be able to
hear using the second radio. I have been able to use Beverage
RX antennas to listen on 40M while transmitting on my beams.
BTW, my TS-830 manual says not to exceed 7(?) Volts (1W) at the
RX antenna input. My old Collins 75A3 had a similar warning
not to exceed 50 Volts (50 Watts !) at the antenna input. You
could almost use the old gear as a dummy load for your exciter
without causing damage! How things change.
de Tom N4KG
On Sat, 20 Jun 1998 17:10:52 -0500 Steve Daniel
>I would like to tap into the collective wisdom and experience of the
>group once again. Is it possible to utilize two radios, one run and
>s&p, on the same band? I was thinking specifically of 15 meters and
>wondering if, with the use of stubs or other sort of filtering, one
>could isolate a portion of the band, say 21250-21300 for example, for
>CQing, while S&Ping the other portions of the band without damaging
>second radio. My particular set up would be using the stacked 5
>monobanders for CQing while using either the high or low tribander for
>S&Ping. The radios are a 950sdx and 950sd. I know that both have
>subreceivers and this approach works, but you can't listen to the S&P
>frequency while the CQ is going and you are using the same antennas
>both frequencies. The CQ antennas and S&P antennas are 200-300 feet
>apart. I appreciate any thoughts or ideas you care to pass along. 73.
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